var test = () => {
  var i
  var arr = ['zce', 38, '大前端'];
  for (i = 0; i < arr.length; i++) {
    console.log(arr[i]);
  }
}

//自增&&存储固定值
var test = () => {
  var i
  var arr = ['zce', 38, '大前端'];
  var len = arr.length;
  for (i = 0; i < len; i++) {
    console.log(arr[i]);
  }
}

//自减
var test = () => {
  var arr = ['zce', 38, '大前端'];
  var len = arr.length;
  while (len--) {
    console.log(arr[i]);
  }
}
